MICHIGAN ACADEMY OF SCIENCE. 



27 



The methods pursued in this and the following analysis were those recommended by 

 Hillebrandi in his treatises on rock analyses. Knowing that much would depend upon 

 the separation of the earth alkalies, the utmost care was exercised in their determination. 

 Their precipitates were in every instance tested spectroscopically and, if necessary, the 

 extraction repeated until in each case they could be considered free from contamination. 

 We may, therefore, regard the results obtained as very accurate. They are as follows: 



The percentages of the oxides of calcium, magnesium, strontium and barium, together 

 with the carbon dioxide and sulphur trioxide, are important. It is at once noticeable 

 that the amounts of strontium oxide and sulphur trioxide are relatively high. A com- 

 parison of the combined molecular ratios of the oxides of calcium and magnesium with 

 that of the carbon dioxide, 



) MgO [imt] '• CO ^ (-89886) = 1 : 1.0014, 



shows that the rock is a dolomite, and in fact a normal dolomite. AVe, thus, have quite 

 conclusive evidence that all of the calcium oxide is, doubtlessl}', present as a carbonate 

 and not in part as a sulphate. 



The unusually large amounts of strontium oxide and sulphur trioxide are extremely 

 interesting. If we consider the small amount of barium oxide present as isomorphous 

 with the srtontium oxide, we obtain the following proportion: 



■) laO cSs) •• SO 3 (.079067) = 1 : 1.0306. 



These values indicate that the sulphur trioxide is combined with the oxides of strontium 

 and barium, and hence, evidence is at hand that the mineral celestite is present in this 

 uppermost stratum to the extent of 14.32 per cent. The results of the analysis are, therefore, 

 in harmony with what has already been said concerning the structure, specific gravity 

 and so forth, thus indicating that the celestite is present in a disseminated condition, 

 doubtlessly, of primary origin. The very small amount of the combined oxides of alumin- 

 ium and iron, namely 0.37 per cent, would preclude any appreciable quantity of pyrite 

 or marcasite being present. It is also significant, as will be seen later, that organic matter 

 and a trace of hydrogen sulphide were noted. 



In the lower strata as already said, the celestite is found lining the cracks and caAaties, 

 and is, of course, of secondary origin.^ It is with these secondary occurrences of celestite 

 that the native sulphur is found. 



Sherzer3 in discussing the origin of the sulphur at this locality rightly refers the same 

 to the hydrogen sulphide, which is to be observed in considerable quantities not only in 

 the water at this quarry but also in the majority of the wells of that section of the county. 

 Sherzer thought that the hydrogen sulphide might be due to the decomposition of pyrite 

 and marcasite, which are supposed to be present in considerable quantities. 



iW. F. Hillebrand. Bulletins 148, and 176, U. S. Geological Survey. 



^E. H. Kraus. "Occurrence and Distribution of Celestite-bearing Rocks," American Journal of 

 Science, XIX, 290, 1905. 



^W. H. Sherzer, "Geological Report on Monroe County," 212, 213, 1900. Also, American Journal 

 of Science 3rd series, L, 246-248, 1895. 



